Thoracic and Complex Aortic Disease

Aortic Dissection Classification

Aortic dissection occurs when an intimal tear allows blood to enter the medial layer, creating a false lumen that propagates along the aorta. It represents one of the most lethal cardiovascular emergencies, with untreated Type A dissection mortality approaching 1% per hour early after symptom onset. ^{[1] [2]}

Stanford Classification

The Stanford system divides dissections based on involvement of the ascending aorta. ^[3]

• Type A: Any dissection involving the ascending aorta, regardless of the site of primary intimal tear. Requires emergent surgical intervention due to high risk of rupture, tamponade, aortic regurgitation, and coronary malperfusion.
• Type B: Dissection confined to the descending aorta (distal to the left subclavian artery). Management depends on presence of complications.

DeBakey Classification

The DeBakey system provides anatomic detail based on origin and extent. ^[4]

• Type I: Originates in ascending aorta and extends to at least the aortic arch, often to the descending aorta or beyond.
• Type II: Originates in and is confined to the ascending aorta.
• Type IIIa: Originates in descending thoracic aorta and extends distally but remains above the diaphragm.
• Type IIIb: Originates in descending thoracic aorta and extends below the diaphragm.

Table 6.2. Aortic Dissection Classification Systems

Temporal Classification

Timing from symptom onset influences treatment strategy and aortic wall characteristics (hyperacute, acute, subacute, chronic) and is used in contemporary guideline frameworks because risks and remodeling potential vary substantially over time. ^{[2] [5]}

Type B Aortic Dissection Management

Type B aortic dissection (TBAD) presents distinct management challenges based on clinical presentation, anatomic extent, and timing, with contemporary practice guided by society guidelines and long-term outcomes studies. ^{[6] [5]}

Complicated versus Uncomplicated TBAD

Complicated TBAD is defined by one or more of the following high-risk features requiring intervention:

• Malperfusion syndrome: Visceral, renal, or limb ischemia from true lumen compression or branch vessel involvement
• Rupture or impending rupture: Hemothorax, periaortic hematoma, rapidly expanding false lumen
• Refractory hypertension: Despite optimal medical therapy with multiple agents
• Refractory pain: Persistent severe back/chest pain suggesting ongoing dissection
• Rapid aortic expansion: Greater than 5 mm growth in less than 6 months
• Maximum aortic diameter exceeding 40 mm during acute phase (predictor of late complications)

Uncomplicated TBAD lacks these features and may be managed with medical therapy alone in the acute setting, though long-term surveillance is mandatory. ^[6]

Medical Management

All patients with TBAD require aggressive blood pressure and heart rate control to reduce aortic wall stress:

• Target systolic blood pressure: Less than 120 mmHg
• Target heart rate: Less than 60 beats per minute to reduce dP/dt

First-line agents include intravenous beta-blockers (esmolol for titratability, labetalol for combined alpha/beta blockade). Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) may be added for rate control. Vasodilators (nicardipine, nitroprusside) address residual hypertension only after adequate heart rate control to prevent reflex tachycardia. ^{[6] [7]}

Pain control with opioids is essential—pain drives sympathetic activation and hypertension, creating a destructive feedback loop.

Long-term medical therapy includes oral beta-blockers, statins for cardiovascular risk reduction, and aggressive management of hypertension. Smoking cessation is critical given the elevated risk of late aneurysmal degeneration. ^[5]

Endovascular Management: TEVAR for TBAD

Thoracic endovascular aortic repair (TEVAR) has become the preferred intervention for complicated TBAD when anatomy permits. TEVAR seals the primary entry tear, redirecting flow into the true lumen and promoting false lumen thrombosis with favorable aortic remodeling. ^[6]

In stable subacute/chronic TBAD, the INSTEAD randomized trial showed no early survival advantage at 2 years with TEVAR plus optimal medical therapy compared with optimal medical therapy alone, while longer follow-up in INSTEAD-XL demonstrated improved aorta-specific outcomes emerging over time, consistent with a remodeling-mediated benefit. ^{[8] [9]}

In acute uncomplicated TBAD, randomized data suggest TEVAR can improve aortic remodeling compared with medical therapy alone, although hard clinical endpoint benefits and optimal patient selection remain areas of active refinement. ^[10]

Indications for TEVAR in TBAD

According to STS/AATS 2022 guidance:

• Definite indication: Complicated TBAD (rupture, malperfusion) with suitable anatomy
• Strong consideration: Uncomplicated TBAD with high-risk features—primary entry tear on outer curvature of arch, false lumen diameter greater than 22 mm, total aortic diameter greater than 40 mm
• May consider: Prophylactic TEVAR in uncomplicated TBAD to reduce late aortic events (evidence evolving)

Technical Considerations

Adequate proximal landing zone (typically ≥2 cm of non-dissected aorta) is essential for secure seal. When the entry tear is in the arch, coverage of the left subclavian artery (LSA) may be required. Elective LSA revascularization is recommended when coverage compromises antegrade flow to reduce posterior circulation stroke, arm ischemia, and spinal cord ischemia risk. ^[11]

Spinal cord protection measures apply when: * Coverage exceeds 20 cm of thoracic aorta * Landing zone is within 2 cm of the celiac artery * Prior abdominal aortic repair exists

The multimodal spinal cord protection bundle includes: CSF drainage (maintain pressure less than 10 mmHg), MAP greater than 80–90 mmHg, hemoglobin optimization (greater than 10 g/dL), and staged procedures when feasible. ^[6]

Persistent false lumen perfusion and partial thrombosis after TBAD are associated with worse late outcomes and help identify patients who require closer follow-up and may benefit from pre-emptive intervention. ^[12]

Type A Aortic Dissection

Type A aortic dissection constitutes a surgical emergency. Without intervention, early mortality is high, driven by aortic rupture, cardiac tamponade, acute aortic regurgitation, coronary malperfusion, or stroke. ^{[1] [13]}

Clinical Presentation

The classic presentation is sudden, severe "tearing" or "ripping" chest pain radiating to the back. However, presentations vary widely:

• Anterior chest pain: Suggests ascending aortic involvement
• Interscapular pain: Suggests arch or descending extension
• Syncope: May indicate tamponade, stroke, or severe hypotension
• Neurologic deficits: Stroke (arch vessel involvement), paraplegia (spinal cord ischemia)
• Limb ischemia: Pulse deficits from iliac extension or obstruction
• Abdominal pain: Visceral malperfusion

Physical examination may reveal blood pressure differential between arms (greater than 20 mmHg), new aortic regurgitation murmur, or signs of tamponade (hypotension, elevated JVP, muffled heart sounds).

Diagnosis

CT angiography (CTA) is the diagnostic modality of choice—rapid, widely available, and highly sensitive and specific. Findings include intimal flap, true and false lumens, and extent of dissection. Transesophageal echocardiography (TEE) is an important adjunct, particularly for assessing aortic valve involvement, pericardial effusion, and coronary ostia. ^{[7] [5]}

Surgical Management

Emergent open surgical repair is the standard of care for Type A dissection:

• Ascending aorta replacement: With or without aortic root replacement (Bentall procedure if root is aneurysmal or valve is incompetent)
• Hemiarch repair: Replacement of the lesser curvature of the arch under hypothermic circulatory arrest
• Total arch replacement: When arch is aneurysmal, torn, or has entry site; requires arch vessel reimplantation

Adjunctive measures include antegrade cerebral perfusion during circulatory arrest to reduce neurologic injury. Contemporary registry data and guideline syntheses support operative repair as the default strategy in eligible patients, with outcomes influenced by malperfusion, age, and center experience. ^{[13] [5]}

Hybrid and Endovascular Approaches

Selected Type A dissections may be candidates for hybrid approaches combining open ascending repair with endovascular arch/descending treatment. Purely endovascular Type A repair remains investigational and is limited to highly selected patients who are prohibitive surgical risks. ^[5]

Complex AAA and TAAA

Planning essentials for complex endovascular repair include careful assessment of sheath access requirements (typically 16–22 Fr), selection of appropriate bridging stents for target vessels (covered or bare-metal based on vessel length and tortuosity), renal protection strategies (hydration, contrast-sparing protocols, and avoidance of nephrotoxic agents), and consideration of staged procedures in extensive 6Thoracic Aortic repairs to reduce spinal cord ischemia risk. Outcomes from experienced centers demonstrate target vessel patency rates typically exceeding 90% at 1–3 years, though endoleak rates remain significant (Type Ia 3–8%, Type II 10–20%) and reintervention rates range from 15–25% at mid-term follow-up. For basic 4Aneurysms repair principles, see 4Chapter 4. ^{[14] [15]}

Thoracic Aortic Aneurysm

• Descending 6Thoracic Aortic: TEVAR is preferred in suitable anatomy, especially in older/high-risk patients; open repair remains for unsuitable anatomy or infection.
• Ascending/arch: Managed with open or hybrid strategies; branched/fenestrated arch endografts are emerging but limited to select anatomy/centers.
• Thresholds: Consider repair at ≥6.0 cm for descending 6Thoracic Aortic (≥5.5 cm with risk factors) and ≥5.5 cm for ascending/arch (lower thresholds with bicuspid valve and risk factors or genetic aortopathy); index to body size in small patients. Connective tissue disorders warrant earlier repair and avoidance of TEVAR when durable proximal/distal fixation is not achievable.
• LSA management: In TEVAR, intentional LSA coverage may be required; plan revascularization electively when possible to mitigate stroke/SCI/arm ischemia.

Landmark endograft studies and contemporary society guidelines support TEVAR as the preferred approach for many descending thoracic aneurysms in appropriate anatomy, while emphasizing individualized threshold selection and connective tissue disorder considerations. ^{[16] [17] [18] [5]}

Ruptured Thoracic Aortic Aneurysm

• Ruptured 6Thoracic Aortic: very high early mortality; TEVAR is preferred for descending rTAA when anatomically feasible due to lower perioperative morbidity vs open repair; open repair for unsuitable anatomy, infection, or genetic aortopathy.
• Technical: Rapid proximal seal; intentional LSA coverage acceptable in emergencies with planned revascularization when indicated; apply spinal cord protection principles as feasible. For vascular trauma management principles, see 16EVTM.

Observational outcomes literature and guideline statements generally favor TEVAR over open repair for ruptured descending thoracic aneurysm when anatomy permits, acknowledging selection bias and the need for rapid hemorrhage control. ^{[19] [18] [2]}

Thoracic aortic aneurysm thresholds (ascending, arch, descending) and genetic disease considerations

Surgical thresholds for the ascending aorta and arch are generally ≥5.5 cm, with lower thresholds in patients with bicuspid valve disease and risk factors or syndromic aortopathy. For the descending aorta, the threshold is ≥6.0 cm, though ≥5.5 cm may be considered with risk factors or rapid growth. The aortic size index should be used in small patients. Earlier thresholds apply in Marfan, Loeys-Dietz, and Ehlers-Danlos syndromes per guidelines, and natural history data support increasing adverse event risk with larger diameters. ^{[5] [2] [7] [20]}

Table 6.1. Thoracic Aortic Aneurysm Repair Thresholds

TAAA classification and spinal cord protection bundle

The Crawford classification helps predict spinal cord ischemia (SCI) risk. Major risk factors include extent of coverage, prior 4Aneurysms repair, hypotension, and coverage of the LSA or IMA. A prevention bundle is recommended, including preoperative risk assessment, selective CSF drainage, maintenance of MAP >80–90 mmHg, hemoglobin optimization, LSA revascularization when feasible, and staged procedures. These principles apply to open, TEVAR, and BEVAR approaches. ^{[21] [22] [23]}

Crawford Classification of TAAA

Open and endovascular series demonstrate that outcomes are strongly influenced by extent (particularly type II), perioperative hemodynamics, and protocolized spinal cord protection. ^{[24] [14]}

Surveillance After Aortic Dissection

All patients surviving aortic dissection require lifelong imaging surveillance regardless of initial treatment strategy. The dissected aorta remains at risk for late complications including aneurysmal degeneration of the false lumen, new dissection, and disease progression. ^{[2] [5]}

Surveillance Protocol

Recommended imaging intervals after dissection or TEVAR:

• 1 month: Baseline post-treatment CTA
• 3 months: Early follow-up to assess remodeling
• 6 months: Intermediate assessment
• 12 months: Annual milestone
• Annually thereafter: Lifelong surveillance
• More frequent imaging if concerning features develop (sac growth, new symptoms, endoleak)

These intervals reflect common guideline-based surveillance patterns intended to detect early complications and late aneurysmal degeneration. ^{[7] [5]}

Favorable Prognostic Indicators

After TEVAR for TBAD, false lumen thrombosis indicates favorable aortic remodeling and is associated with reduced late adverse events. Complete thrombosis of the thoracic false lumen is the goal; persistent perfusion of the false lumen via distal re-entry tears may limit remodeling, and partial thrombosis has been associated with worse outcomes in dissection cohorts. ^{[9] [12]}

Medical Optimization During Surveillance

Lifelong medical therapy is essential:

• Blood pressure control (target less than 130/80 mmHg)
• Beta-blockade to reduce wall stress
• Statin therapy for cardiovascular risk reduction
• Smoking cessation (strongly emphasized)

Patients with connective tissue disorders require genetic counseling and family screening. First-degree relatives should be offered imaging surveillance given familial clustering of thoracic aortic disease. ^[6]